2-D interpolation for HC11

[Bruce Bowling]

~ Hi Bruce,
~ I have some table interpolation code for the HC11 however it is a 1-D 
~ table with 16 bit values. The code is optomised inline assembler for 
~ the HITECH-C compiler. The code has been tested thoroughly - I 
~ sumulated every boundary condition and it allows for positive and 
~ negative slope in the map. I started to write a 2-D map but I didn't 
~ really need it at the time...
~ I'll send the code if you think it may be useful.
~ 
~ Andrew
~ 
Yes, I will take a copy - I am sure can use it.

Researching into the 2-D interpolation problem, the "cleanest"
algorithm that I have found to date is in the Handbook of
Mathematical Functions by Abramowitz and Stegun, which uses
the 4-point method:

f(x0+ph, y0+qk) = (1-p) * (1-q) * f(0,0)   +   p * (1-q) * f(1,0) +
		  (1-p) * q * f(0,1)       +   p * q * f(1,1)
with:
x0, y0 = some arbitrary baseline (D.C. offset)
p = normalized 1st coordinate value (ranging from 0 to 1)
p = normalized 2nd coordinate value (ranging from 0 to 1)
f(0,0) = function value at grid point coordinate (0,0)
f(0,1) = function value at grid point coordinate (0,1)
f(1,0) = function value at grid point coordinate (1,0)
f(1,1) = function value at grid point coordinate (1,1)

There are 5, 6, and 7 point formulas as well, but more complicated.

Anyone out there know of anything else more suited for
integer or fixed-point math?

Thanks again, Andrew

- Bruce

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               Bruce A. Bowling
  Staff Scientist - Instrumentation and Controls
 The Continuous Electron Beam Accelerator Facility
    12000 Jefferson Ave - Newport News, VA 23602
                 (804) 249-7240
                bowling at cebaf.gov  
        http://devserve.cebaf.gov/~bowling
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